In recent years, highly computerized vehicles have been provided with driving assistance devices for assisting the driving such as a VSC (vehicle stability control) system and an ACC (adaptive cruise control) system. Such driving assistance devices detect a running state of the vehicle based on detection results of various sensors such as a yaw rate sensor and a wheel speed sensor, and determine a control scale of an actuator that is a drive source of the drive train of the vehicle based on the detection results. Based on the determined control scale, the magnitude of engine braking is controlled, a brake force of the brake is controlled or an assist force applied to the steering wheel is controlled, and the drive train of the vehicle is controlled. According to this, the safety of the operation of the vehicle is improved, and fuel economy is improved through economical driving assistance.
To reliably assist driving, high reliability is required for the control scale of the actuator, a reference value for determining the control scale, in other words, detection values of the sensors. Hence, the reliability for the control scale is ensured by making a control device for calculating the control scale into a duplexed system, or by calculating the control scale by a plurality of mutually different processing operations as shown in Patent Document 1. A device described in Patent Document 1 includes main control means provided with “second processing means”. The second processing means calculates the control scale based on detection results of various sensors that detect a running state of a vehicle, and a driving state of an actuator is controlled based on the control scale obtained by the main control means. This device includes, in addition to the main control means, “first processing means”, which takes in at least one detection result of the various sensors and calculates the control scale through simple processing, which is different from the main control means. Total two control scales calculated by the first and second processing means are compared with each other, and if the comparison results are different from each other, it is determined that the reliability of the control scales is low, and operation of the actuator conducted by the main control means is inhibited.
A device described in Patent Document 2 determines the reliability of running environment information of a vehicle detected by various sensors, and driving modes are switched between automatic driving and manual driving in accordance with the reliability.